Question

So I’m using Word.Interloop and in order to compare two pics, I guess I have to transform the current picture(in word file) to a bitmap image and then compare it with a bitmap image object from desktop?
Or perhaps the is a simpler way to do so?

Word.InlineShape x;
x.isEqual( Picture from Desktop/ bitmapImage.Object);

Answer 1

I have made a small sample showing how this can be accomplished. The main idea is to represent your image from your desktop as a Bitmap instance and then compare it pixel by pixel to the Bitmap instance in your document. The comparison is done by first copying an inline shape to the clipboard, then turning it into a Bitmap, and then compare it with the reference (from the desktop) – first by size and then pixel by pixel.

The sample is implemented as a C# console application using .NET 4.5, Microsoft Office Object Library version 15.0, and Microsoft Word Object Library version 15.0.

using System;
using System.Drawing;
using System.Threading;
using System.Windows.Forms;
using Application = Microsoft.Office.Interop.Word.Application;

namespace WordDocStats
{
    class Program
    {
        // General idea is based on: https://stackoverflow.com/a/7937590/700926
        static void Main()
        {
            // Open a doc file
            var wordApplication = new Application();
            var document = wordApplication.Documents.Open(@"C:\Users\Username\Documents\document.docx");

            // Load the image to compare against.
            var bitmapToCompareAgainst = new Bitmap(@"C:\Users\Username\Documents\image.png");

            // For each inline shape, do a comparison
            // By inspection you can see that the first inline shape have index 1 ( and not zero as one might expect )
            for (var i = 1; i <= wordApplication.ActiveDocument.InlineShapes.Count; i++)
            {
                // closure
                // http://confluence.jetbrains.net/display/ReSharper/Access+to+modified+closure
                var inlineShapeId = i; 

                // parameterized thread start
                // https://stackoverflow.com/a/1195915/700926
                var thread = new Thread(() => CompareInlineShapeAndBitmap(inlineShapeId, bitmapToCompareAgainst, wordApplication));

                // STA is needed in order to access the clipboard
                // https://stackoverflow.com/a/518724/700926
                thread.SetApartmentState(ApartmentState.STA);
                thread.Start();
                thread.Join();
            }

            // Close word
            wordApplication.Quit();
            Console.ReadLine();
        }

        // General idea is based on: https://stackoverflow.com/a/7937590/700926
        protected static void CompareInlineShapeAndBitmap(int inlineShapeId, Bitmap bitmapToCompareAgainst, Application wordApplication)
        {
            // Get the shape, select, and copy it to the clipboard
            var inlineShape = wordApplication.ActiveDocument.InlineShapes[inlineShapeId];
            inlineShape.Select();
            wordApplication.Selection.Copy();

            // Check data is in the clipboard
            if (Clipboard.GetDataObject() != null)
            {
                var data = Clipboard.GetDataObject();

                // Check if the data conforms to a bitmap format
                if (data != null && data.GetDataPresent(DataFormats.Bitmap))
                {
                    // Fetch the image and convert it to a Bitmap
                    var image = (Image)data.GetData(DataFormats.Bitmap, true);
                    var currentBitmap = new Bitmap(image);
                    var imagesAreEqual = true;

                    // Compare the images - first by size and then pixel by pixel
                    // Based on: http://www.c-sharpcorner.com/uploadfile/prathore/image-comparison-using-C-Sharp/
                    if(currentBitmap.Width == bitmapToCompareAgainst.Width && currentBitmap.Height == bitmapToCompareAgainst.Height)
                    {
                        for (var i = 0; i < currentBitmap.Width; i++)
                        {
                            if(!imagesAreEqual)
                                break;

                            for (var j = 0; j < currentBitmap.Height; j++)
                            {
                                if (currentBitmap.GetPixel(i, j).Equals(bitmapToCompareAgainst.GetPixel(i, j)))
                                    continue;

                                imagesAreEqual = false;
                                break;
                            }
                        }
                    }
                    else
                    {
                        imagesAreEqual = false;
                    }
                    Console.WriteLine("Inline shape #{0} is equal to the 'external' bitmap: {1}", inlineShapeId, imagesAreEqual);
                }
                else
                {
                    Console.WriteLine("Clipboard data is not in an image format");
                }
            }
            else
            {
                Console.WriteLine("Clipboard is empty");
            }
        }
    }
}

References:

• Threadstart with params: https://stackoverflow.com/a/1195915/700926
• Extracting inline shapes as images from word in C#: https://stackoverflow.com/a/7937590/700926
• Comparing images in C#:
  http://www.c-sharpcorner.com/uploadfile/prathore/image-comparison-using-C-Sharp/
• Details on how to retrieve an image from the clipboard in C#: https://stackoverflow.com/a/998825/700926
• Details on how to access the clipboard from C#: https://stackoverflow.com/a/518724/700926